1. Field of the Invention
This invention relates to a projection exposure apparatus and a projection exposure method which are used, for example, when a micro device such as a semiconductor integrated circuit, an imaging element such as a CCD or the like, a liquid crystal display, a thin film magnetic head, or the like is fabricated by using lithography technology, and to a projection optical system which is suitable for use in the projection exposure apparatus.
2. Related Background Art
Recently, as circuit patterns of micro devices such as semiconductor integrated circuits and the like have been made smaller, a wavelength of illumination light (exposure light) for exposure which is used in an exposure apparatus such as a stepper has been shortened. That is, as exposure light, instead of an i line (wavelength: 365 nm) of a mercury lamp which was mainly used in a conventional device, KrF excimer laser light (wavelength: 248 nm) is mainly used. Furthermore, ArF excimer laser light which has an even shorter wavelength (wavelength: 193 nm) has been made practical. Additionally, with the object of developing exposure light of a short wavelength, use of halogen molecular laser or the like such as F2 laser (wavelength: 157 nm) is also being tested.
As a light source at a wavelength 200 nm or less in a vacuum ultraviolet region, the above-mentioned excimer laser, halogen molecular laser, or the like can be used. However, there is a limit to practically developing a narrow band in such lasers. Additionally, materials which transmit radiated light in a vacuum ultraviolet region are limited, so only limited materials can be used for the lens elements which constitute the projection optical system. The transmittance of these limited materials is not very high. Furthermore, currently, performance capability of antireflection coatings provided on a surface of the lens elements is not as high as in long wavelength light.
Therefore, one object of this invention is to have a short glass path length and a low number of lens surfaces, to suitably correct chromatic aberration, and to reduce a burden of a light source. Furthermore, another object of this invention is to suitably project and expose an image of a pattern of a mask which has been made extremely fine onto a workpiece.
To accomplish the above-mentioned objects, a projection optical system of a first embodiment is a dioptric projection optical system which projects an image of a first surface onto a second surface, includes lens components formed of at least two types of fluorides, and is constituted by, in order from the first surface side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having an aperture stop within an optical path, and a fifth lens group having a positive refractive power. An clear aperture of a light beam in the projection optical system is at a maximum within the second lens group, is at a minimum within the third lens group, is at a relative maximum within the third, fourth, or fifth lens groups, and has only one significant minimum between the first surface and the second surface.
Additionally, in order to accomplish the above-mentioned object, the projection optical system of a second embodiment is a dioptric projection optical system which projects an image of a first surface onto a second surface and is constituted by, in order from the first surface side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having an aperture stop within an optical path, and a fifth lens group having a positive refractive power. When an clear aperture of a light beam in the projection optical system monotonically increases within the first lens group in the direction from the first surface side to the second surface side, the clear aperture of the light beam goes from an increased size to a decreased size within the second lens group, the clear aperture goes from a decreased size to an increased size within the third lens group, the clear aperture monotonically decreases within the fifth lens group, the clear aperture of a surface having the maximum clear aperture within the second lens group is Mx2, and the clear aperture of a surface having the minimum clear aperture within the third lens group is Mn3, and the following condition is satisfied:
1.7 less than Mx2/Mn3 less than 4.
Additionally, in order to accomplish the above-mentioned object, a projection exposure apparatus according to this invention is a projection exposure apparatus which projection exposes an image of a pattern arranged in a mask onto a workpiece, is provided with a light source which supplies exposure light, an illumination optical system which guides exposure light from the light source to the pattern on the mask, and the projection optical system, and can arrange the mask at the first surface and the workpiece at the second surface. Furthermore, in preferred embodiments of the projection exposure apparatus of this invention, the light source supplies exposure light in a vacuum ultraviolet region, and in further preferred embodiments, the light source includes an F2 laser.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.